Yamaha Raptor Race Motor.....how much can I use?

[Demolition Man]

My friends all race flat track on their four wheelers....my business partner and his friend race Yamaha Raptors....they are getting over 75hp at the wheels....they are going for 100hp and will sell me their old race motor with a fresh rebuild....dual 39mm carbs, stage 3 cam, 105mm 14:1 piston, stroked falicon crank, forged rod, big valve head with Ti valve train and heavy porting, machined cases for stroke clearance, HD clutch, basket, and springs, and a dyna adjustable ignition set at 11,000 rpm along with a custom stepped header that I will have to modify to fit the MZ by the looks of it with w Ron Woods Can off a YFZ450 quad....well I guess my question is can I just pull the whole top end of this race motor off, carbs and all, and slap it on the MZ with the Dyna Ignition and will the stroker crank and rod work in the MZ or will I have to stroke the crank in the MZ....and if the stroker is used will the MZ need clearancing like the raptor? I can basically get this motor for a song and the customizing of the exhaust can be done for free by my friend who builds custom choppers...so its not the expense I am concerned about it is the feasibility of the grafting I am worried about....I have ridden the quad with this motor down the back roads a few times and if this motor was in the MZ I would be able to down right compete with any 600 supersport up to say 120mph or so....when the road opens up a little.....and the 3rd gear power wheelies will hopefully transfer from the quad to the bike...BTW how about the race clutch set up...will that work too?

[phlat65]

the bottom end cases are different than our engine. I would try to install the engine in the MZ chassis first, before you try to swap all the motor stuff out. from my understanding, the engines are the same from the cylinder up, except the raptor valve train and cam grind.

our engine revs to 7500 rpm or so. to have another 3500 rpm would change the bike sooooo much!

having the raptor clutch set up would be better, I think it is easier to service trackside.

If you don't buy the engine, I have first dibs

[Demolition Man]

I would consider just putting the motor in, but the four wheeler has reverse, and an external oil filter that sticks out, and I would guess that the gear ratios in the tranny would be shorter in the quad....if the motor parts will work easily then I would just do a part swap and tune...

[oldboyonrgv]

U will have to use the crankcase and gearbox from the bike then build everything into those cases, if its a stroker crank you will have to have the cases relieved, don't be tempted to run the standard crank it will let go !

[oldboyonrgv]

By the way, a slipstream tuned and stroked 720 motor produces 83BHP and runs to 9000RPM, re-builds are every three meetings, at 9200 the engine grenades, I cannot believe that you can get these engines to turn at 11000RPM .

[keithcross]

The Raptor uses a different,lighter crank (flywheels are round on the MZ engine, they arent on teh Raptor) and lighter titanium valves. This allows th eengine to run at higher revs.

[Demolition Man]

So in order to run at the higher rpm will I need to lighten the crank and flywheel on the MZ to around the same weight of the Raptor?.....will the Raptor flywheel work/fit the MZ? and if I brought the stock crank to racing crank builder and had it lightened and knife-edged would that suffice to handle the higher revs? These bikes deserve to have MOTOR....and I believe they will handle it well. I really want to catch sportbikes sleeping on straights too..not just twisties.... And FYI a bone stock Raptor turns 9000rpms all day long....that is where the rev limiter kicks in....keeping all else stock, just putting in a rev box gives you 10500rpm reliably on a stock motor...the dyna ignition will give you up to around 14000rpm for a raptor sand drag motor to use...not to mention provisions for nitrous tuning and turbo/supercharger tuning..now imagine how fast a 14000rpm MZ would go with the stock gearing.....hey my friends are going for 100hp on their Raptors and they will get there as it was already done....how bout a 100hp MZ that can reach 150MPH....now thats a DIRT bike!!!! See where I am going....

[F0ul_Oli]

[oldboyonrgv]

Take it from me, you wouldn't want to go much above 110MPH on one of these, they get very unstable !
I agree with F0ul_Oli the whole point of em is Torque not revs.

[Demolition Man]

well 150mph I know is not really attainable.....but I like sleepers....it is more fun to make something a one of a kind then to just go out and buy the fastest bike out....I already have a very fast sportbike.....very fast quad....very fast dirt bike....now I want my motard to be equally as fast as at least my KX500(which is my next street project....)and if I hadn't ridden my friends race Raptor then I would have thought this improbable...but I did and here I am just seeking what his now "slow" motor has for my MZ.....if you rode any bike with that motor it would be very exciting.....the bottom is stronger than stock but when you hit the mid-top rpm range the thing straight hauls and revs like a two-stroke.....just as you said...and that would make the MZ extraordinary...

[Demolition Man]

opened up my friends motor and it was not in good shape....cylinder scored, cracks in head between valves which were burnt pretty bad, and detonation marks all over top of piston...how it was still running as well as it seemed is beyond me.....so I called up Trinity Racing...these guys are really interested in modding out MZ's....they build some of the fastest drag quad motors in the business....two-strokes and four strokes alike....after much deliberation we (me and David from Trinity) decided their Max Power 686 (which they have done hundredes of) would be the best choice for Power -vs- Reliability on the street where you can run the motors wide open for extended periods....they are seeing over 75 rwhp from this setup which is fairly inexpensive for what is done...they require you to send the top end, carbs, and ignition/cdi...what you get back is a big valve ported head w/all the goodies, a custom to application cam, 39mm FCR carb kit with their own intake box and adaptors, 102mm hicomp JE piston, and a Dyna ignition/cdi box with their own custom map....for under 3k it is a relative bargain considering the carb kit alone with their custom parts is 1200.00...check them out at www.trinityracing.com or call 1-877-327-8697 and Talk to David....tell him Jeff from NY told you about it so they know there is an interest in the aftermarket for MZ's.....

[phlat65]

sounds great! are they using 1 carb? there is a kit from tunebike that uses 2 flatslides.

[Demolition Man]

no it is a dual 39mm carb kit....not single...they say on a heavily breathed on motor the single carb kits rob a few HP and are hard to tune...

[jamboa]

They do all those top end mods and keep the stock Raptor con rod. Is the rod the same as the Baggy/ I have heard several times on this board that if you go big bore you need a Carillo oother stronger rod. I would like to do a street job big bore Wiesco 686 with stock cam. Will the stock rod hold up on the long term on the street?

[steveweck]

Just rec'd my Hot Rods heavy duty crank assembly today. This is made for the Raptor. It's completely assembled with the heavey duty con rod. I'm experimenting with this for my Skorpion project/race bike. I've been accumulating several motor parts and should start taking the bottom end of the motor apart this week. So far I have the Edelbrock single carb kit which includes the manifold. It's a big sucker. I've also cleaned up the cylinder head lightly and installed new valves from Kibblewhite. I've installed the Hot Cams spring kit which are needed for when the Hot Cams Stage 2 cam goes in upon reassembly. My cylinder is bored 2mm over to accept the 102mm Wiseco high compression piston. This is why the con rod needs to be upgraded.

At first I was going to just have the Hot Rods con rod installed. I've assured it fits. However, that involves complete diassembly of the motor and the crank itself. Buying the complete crank assembly eliminates the crank work which reduces time and money spent. It wasn't a whole lot more than just the con rod. Now I have half the work done and I'm sure its done right. I still need one bearing that wasn't included but thats easy to measure and order. The crank is supposed to fit and turn with out a problem but I understand I'll have to figure something out with the flywheel. Maybe I'll get rid of it along with any other metal I can remove.

As far as performance gains from the Hot Rods kit are concerned I'm not sure if there are any weight saving. Its a different shape but I'll need to weigh both assemblies to compare. It is stronger then the stock set up and the complete assembly is still cheaper than a Carillo rod alone.

Just a comment about torque and horsepower. I don't think reducing the weight of engine parts takes away any torque nor does it make torque. Displacement and compression make torque and horsepower. There are however other advantages gained by reducing weight. Handling the improved if there is less gyro effect from the motor. Braking is also improved with less weight spinning forward. Assuming the parts that are being lightened are also being strengthened you will be reducing stress in the motor and reducing frictional loses. The lighter parts will allow the motor to rev quicker which I believe to be more important than reving higher. You want to get into the meat of your torque curve as soon as possible. Peak horsepower is meaningless in most racing and street riding situations. Heres an example:

Two bikes are exiting a 2nd gear corner at the same time leading onto a quarter mile straight which then leads to another 2nd gear corner. One bike (a) make 110hp and 45lbs of torque. The second bike (b) makes 95hp and 60lbs of torque. If all else is equal bike (b) should be able to get into the next corner first. Bike (b) should be able to get up to its max. speed per gear sooner then bike (a). Even though bike (a) makes more peak power (b) has the advantage. It be in front and doing 10-15 mph faster sooner, opening a gap. Bike (a) with its hp advantage will surely gain back the gap with its higher top speed but it will be to late. Bike (b) will have already turned into the next corner. Another advantage bike bike (b) has is its lack of top speed compared to (a). Bike (b) the "slower" bike didn't need to slow down as much to make the corner. As a result he was able to carry way more corner speed further increase his advantage over bike (a). Bike a in order to catch (b) on the straight had to use his top speed all the way to the corner and then he had to brake much harder to slow down enough to make the corner. Usually this results in over braking and losing lots of corner speed. It also upsets the chassis and makes turning in physically harder and less safe and slow.

After saying all that, I agree with the statement that, If you want to "go" fast bike buy a fast bike. But I'd like to add, If you want to "be", fast find a track day and ask for help.

Hey Demo Man where are you in NY?

Steve Weckesser